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membarrier.h
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#ifndef _LINUX_MEMBARRIER_H #define _LINUX_MEMBARRIER_H /* * linux/membarrier.h * * membarrier system call API * * Copyright (c) 2010, 2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ /** * enum membarrier_cmd - membarrier system call command * @MEMBARRIER_CMD_QUERY: Query the set of supported commands. It returns * a bitmask of valid commands. * @MEMBARRIER_CMD_GLOBAL: Execute a memory barrier on all running threads. * Upon return from system call, the caller thread * is ensured that all running threads have passed * through a state where all memory accesses to * user-space addresses match program order between * entry to and return from the system call * (non-running threads are de facto in such a * state). This covers threads from all processes * running on the system. This command returns 0. * @MEMBARRIER_CMD_GLOBAL_EXPEDITED: * Execute a memory barrier on all running threads * of all processes which previously registered * with MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED. * Upon return from system call, the caller thread * is ensured that all running threads have passed * through a state where all memory accesses to * user-space addresses match program order between * entry to and return from the system call * (non-running threads are de facto in such a * state). This only covers threads from processes * which registered with * MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED. * This command returns 0. Given that * registration is about the intent to receive * the barriers, it is valid to invoke * MEMBARRIER_CMD_GLOBAL_EXPEDITED from a * non-registered process. * @MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED: * Register the process intent to receive * MEMBARRIER_CMD_GLOBAL_EXPEDITED memory * barriers. Always returns 0. * @MEMBARRIER_CMD_PRIVATE_EXPEDITED: * Execute a memory barrier on each running * thread belonging to the same process as the current * thread. Upon return from system call, the * caller thread is ensured that all its running * threads siblings have passed through a state * where all memory accesses to user-space * addresses match program order between entry * to and return from the system call * (non-running threads are de facto in such a * state). This only covers threads from the * same process as the caller thread. This * command returns 0 on success. The * "expedited" commands complete faster than * the non-expedited ones, they never block, * but have the downside of causing extra * overhead. A process needs to register its * intent to use the private expedited command * prior to using it, otherwise this command * returns -EPERM. * @MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED: * Register the process intent to use * MEMBARRIER_CMD_PRIVATE_EXPEDITED. Always * returns 0. * @MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE: * In addition to provide memory ordering * guarantees described in * MEMBARRIER_CMD_PRIVATE_EXPEDITED, ensure * the caller thread, upon return from system * call, that all its running threads siblings * have executed a core serializing * instruction. (architectures are required to * guarantee that non-running threads issue * core serializing instructions before they * resume user-space execution). This only * covers threads from the same process as the * caller thread. This command returns 0 on * success. The "expedited" commands complete * faster than the non-expedited ones, they * never block, but have the downside of * causing extra overhead. If this command is * not implemented by an architecture, -EINVAL * is returned. A process needs to register its * intent to use the private expedited sync * core command prior to using it, otherwise * this command returns -EPERM. * @MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE: * Register the process intent to use * MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE. * If this command is not implemented by an * architecture, -EINVAL is returned. * Returns 0 on success. * @MEMBARRIER_CMD_SHARED: * Alias to MEMBARRIER_CMD_GLOBAL. Provided for * header backward compatibility. * * Command to be passed to the membarrier system call. The commands need to * be a single bit each, except for MEMBARRIER_CMD_QUERY which is assigned to * the value 0. */ enum membarrier_cmd { MEMBARRIER_CMD_QUERY = 0, MEMBARRIER_CMD_GLOBAL = (1 << 0), MEMBARRIER_CMD_GLOBAL_EXPEDITED = (1 << 1), MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED = (1 << 2), MEMBARRIER_CMD_PRIVATE_EXPEDITED = (1 << 3), MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED = (1 << 4), MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE = (1 << 5), MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE = (1 << 6), /* Alias for header backward compatibility. */ MEMBARRIER_CMD_SHARED = MEMBARRIER_CMD_GLOBAL, }; #endif /* _LINUX_MEMBARRIER_H */